On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 499 
The specimens figured are from the collection of the Earl of Enniskillen and the 
Reed collection at York. 
locality, near Richmond, in Yorkshire. 
The fine specimen, represented on Pl. LIX., fig. 
In each case they have been obtained from the same 
22, exhibits a peculiar form 
of the root, which is deeply grooved in a loavetine ell direction, and appears to 
approach, in some degree, to the divided root of Polyrhizodus. 
In the same speci- 
men the folds which encircle the base of the crown are united, and form a single 
prominent overlapping plication. 
Formation and locality : Mountain Limestone. 
Ex coll. Earl of Enniskillen, and Reed Collection, York Museum. 
Petalodus rectus, Agass. 
(Pl. LX., fig. 5.) 
Petalodus rectus—L. Agassiz, 1840. ‘Rech. sur les Poiss. Foss.,” Vol. IIT., pp. 174 and 384, 
ty » J. E. Portlock, 1843. “Geol. of Londonderry,” &c., p. 461, pl. xiv., fig. 9. 
a % C. G. Giebel, 1843. ‘Fauna der Vorwelt,” Vol. I., pt. 3, p. 345. 
. oy H. G. Bronn, 1848. ‘Nomencl. Paleont.,” p. 949. 
- % 3 1849. “ Enumerator Paleont.,” p. 646. 
5) % J. Morris, 1854. “Cat. Brit. Foss.,” p. 337. 
Es 5 F. J. Pictet, 1854, “Traité de Paléont.,” Vol. II., p. 271. 
s s F. M‘Coy, 1855. “Brit. Paleoz. Foss.,” p. 636, 
Young & Armstrong, 1871. 
“ Trans. Geol. Soc. Glasgow,” Vol. ITI., Supt., p. 74. 
Armstrong, Young, 
and Robertson, 1876. ‘Cat. of W. Scot. Foss.,” p. 62. 
Teeth ; “ Very broad, greatly flattened ; crown thin, rectilinear, or nearly so ; in 
some specimens slightly undulated, and marked with vertical strie near the edge, 
in others, crown surrounded by a broad band of four or five imbricating lamellee 
of ganoine; root deeper than the crown and coronal folds together, concave in its 
upper half, tumid and longitudinally rugged below. Average length of a rather 
small specimen 1 inch; height of crown 1 line, width of coronal bands # line, depth 
The width and slight elevation of the knife-like crown of this 
The name of P. rectus of Agassiz’s 
of root 24 lines. 
species easily distinguish it from any others. 
published lists applies to the perfect, nearly straight-edged specimens, while his 
name P. marginalis applies to the slightly-worn examples, in which the edge is 
striated and undulated, and I have traced the perfect passage of one form to the 
other.’ —(MCoy.) 
This species is figured by J. E. Portlock, in the ‘‘ Geological Report of 
Londonderry,” &c., pl. xiv., fig. 9. It approaches very nearly in form to the genus 
Chomatodus, as defined by Messrs. Newberry and Worthen (“ Paleont., Illinois,” 
Vol. IL. p. 34), excepting the root, which is well developed, and petalodont in 
character. 
Formation and locality : Carboniferous Limestone, Lowick. 
TRANS. ROY. DUB, SOC,, N.S., VOL. I. 4G 
